This invention relates to apparatus for splitting or breaking up rock, and more specifically to such a rock splitter having a slider wedge slidably engaged between a pair of presser cheeks and actuated hydraulically for wedging the presser cheeks apart from each other in a drill hole.
In a hydraulic rock splitter of the type under consideration, as heretofore constructed, the slider wedge is rigidly coupled to the depending piston rod of a hydraulic cylinder assembly, whereas the pair of presser cheeks are connected to the cylinder body of the cylinder assembly via two opposed pairs of leaf springs. The presser cheeks together with the slider wedge therebetween is inserted in a drill hole created in the ground. Upon forced descent of the slider wedge by the cylinder assembly, the leaf springs restrain the presser cheeks from longitudinal displacement but allow them to move apart from each other for splitting or breaking up the rock. The leaf springs serve the additional purpose of elastically holding the presser cheeks in proper engagement with the slider wedge.
This known type of rock splitter has several problems arising from the configuration of the leaf springs and their connections to the cylinder body and to the presser cheeks. First of all, as each pair of opposed leaf springs has been spaced a considerable distance from each other, they have been susceptible to great bending stresses when the presser cheeks connected thereto are subjected to uneven tensile forces as by the movements of the split rock. The bending stresses act not only on the leaf springs but also on the slider wedge and the presser cheeks, possibly causing their deformation.
Another problem also manifests itself upon descent of the slider wedge. Each pair of opposed leaf springs tend to spread apart into a flaring shape when the presser cheeks move away from each other upon descent of the slider wedge. In the prior art rock splitter, however, the presser cheeks have their top end portions keyed to the opposite sides of the slider wedge. The keys restrict the spreading motion of the presser cheeks with respect to the wedge. Consequently, as each pair of opposed leaf springs tend to spread apart into a flaring shape as above, their lower end portions, connected to the presser cheeks, are forced to bend toward each other, with the consequent exertion of substantial bending stresses on the keys. The useful life of the keys has therefore been very short.
A further problem of the prior art arises at the time of the withdrawal of the slider wedge following the splitting of the rock. The leaf springs experience longitudinal compressive stresses as the slider wedge is pulled upwardly in sliding contact with the presser cheeks. The greater the frictional resistance offered by the presser cheeks against the upward travel of the slider wedge, the more are the longitudinal compressive stresses on the leaf springs. The leaf springs have conventionally been rigidly coupled to both the cylinder body and the presser cheeks. Thus the compressive stresses have been easy to build up to such an extent as to cause the buckling and, in the worst case, destruction of the leaf springs. The exertion of compressive forces on the leaf springs and the presser cheeks can also take place in the act of rock splitting. On being fractured by the wedging action of the rock splitter, the rock tends to be displaced upwardly. The upward thrust thus imparted to the presser cheeks has been another reason for the possible breaking of the leaf springs and presser cheeks under compression.